Pursuant to existing government regulations any motor vehicle manufactured after 1952, and having a body with a clearance at the rear end of more than 30 inches from the ground when empty, must be provided with bumpers or devices serving similar purposes constructed and located so that the clearance between the effective bottom of the "bumpers" and the ground does not exceed 30 inches with the vehicle empty and the "bumper" should not be located more than 24 inches forward of the extreme rear of the vehicle. This regulation was put into effect to prevent the front ends of smaller passenger vehicles from driving underneath a bed of a truck and potentially causing harm to the passengers upon the truck breaking through the front window of the passenger vehicle.
Dump trucks which have boxes which overhang the rear axles and extend rearwardly thereof provide a hazard for rear end collisions, particulary those in which the impact is moderate and the occupants of the rear vehicle involved in the rear end collision are exposed to impact with the base of the box of the dump truck. In particular, rear end collisions of this type expose the occupants of the oncoming rear vehicle to extremely hazardous conditions, since the oncoming vehicle frequently will find no significant abutment surface until the forward portion of the oncoming passenger vehicle strikes the axle housing or the rear wheels of the dump truck. Therefore, the government has the mandated "bumper" locations to address this problem.
When arranged in an overhanging relationship, upon dumping, the rear or tailgate portion of the truck which meets these regulations will extend or pivot downwardly toward the ground, and in doing so would bend, break, or possible destroy any bumper which may be disposed there.
On the other hand, if a bumper was arranged at the position which would not interfere with the normal dumping operation, such a bar would provide little if any protection for the occupants of oncoming vehicles, since it would necessarily be disposed at a substantial elevation from the ground.
Trucks which have fixed length conventional beds do not present significant problems, in much as the bed is fixed relative to the truck frame and thus providing such trucks with a bumper is not a problem.
Because trucks of the present invention typically are more than 30 inches off the ground, they are encompassed by the regulations. The contemplated vehicles employ extendible beds, which are disposed on a tilt frame; while it would be desirable for bumpers to be much lower than 30 inches and to be positioned closer than 24 inches to the rear of the bed supporting structure, doing so would make it impossible to tilt the platform or bed without having the bumper contact the ground and be bent or destroyed. Several types of load carrier vehicles are provided with a load carrying member which is tiltable to receive a load and to discharge a load. If such a vehicle travels on the highways and streets it is necessary for the vehicle to include a bumper to protect other vehicles as previously described. Ordinarily, the only suitable location for a bumper is as a part of the tiltable load carrying member. However, a problem exists, in that a bumper fixedly attached to the tiltable load carrying member may engage the ground and interfere with the tilting of the load carrying member.
In certain congested areas, such as Boston, Mass., or in some receiving/loading docks, a fixed length tiltable load carrying member is problematic. A driver normally prefers to drive a truck with a short bed length. This reduces gas consumption and allows access to "limited" areas. However, if the load which is to be picked up is lengthy, it is necessary to drive a truck with a corresponding bed length. Furthermore, even if the short bed length is sufficient to carry the load, some receiving/loading docks may have height restrictions which do not allow the bed to tilt up to its maximum angle in order to receive or drop the load. For at least these reasons, it is desirable to provide a truck having an extendible, as well as tiltable, bed.
There have been some efforts to resolve the problems associated with bumpers on tilt bed trucks such as fastening bumpers to the rear of the truck in a way that allows them to be quickly disconnected either altogether or in part, and folded to a retracted position before the bed of the truck is tilted. This is still a problem, since it is easy to forget to attend to the bumpers, which are accordingly bent or destroyed when the bed of a roll off truck is tilted. These types of bumpers are typically not adjustable to accommodate changes in regulations, and typically require a driver to get in and out of the cab to move the bumper and then tilt the bed.
Vehicles with a tiltable load carrying member with an attached bumper have also been provided with means to move the bumper from its active or extended position to permit tilting the load carrying member to its maximum position without interference by the bumper. Such means for moving the bumper typically have required separate actuator members for moving the bumper from its active extended position to an inactive retracted position. Also, a pair of actuator members are normally employed, one on each end of the bumper, often resulting in uneven deployment of the bumper, and even damage to the bumper and/or both actuators if one actuator is not functioning. These devices, some of which are automatically activated when the bed begins to tilt up or down, can be quite expensive to add to a new or existing truck. In the event of an electrical or mechanical failure in the device, irreparable damage to the device could occur from a tilt bed tilting on the device, unbeknownst to the driver. Such damage would then require costly repair or replacement procedures which also would take the truck off the road for extended periods of time.
Thus, there is a need for a simple, low cost extendible rear bumper for a truck having tiltable and extendible bed, wherein the extendible rear bumper is attached to the frame of the truck. There is also a need for an extendible bumper with an adjustable height mechanism so that the entire bumper need not be replaced as federal regulations change. There is also a need for an extendible bumper with an indication means so that the driver of the truck will know when the bumper is in its retracted position. There is a further need for an extendible bumper which extends and retracts steadily from the rear of the truck, and remains parallel with the rearmost bar of the truck frame. There is further the need to provide an extendible rear bumper which is easy to repair.